I have ilmberger "street" carbon pieces. The belly pan is a single piece and is made for stock cat and the stock sidestand.

The Sargent seat IS way more comfortable than the stock seat. It very naturally keeps me about 3" back off the tank without any effort and I can slide back or off to the side as needed with no problem.

From my homework reading plenty on this forum, it looks like about 95% visual / cool looking with pretty much the same sound as the stock can. Little bit of weight savings. I did the exhaust valve mod which beefed up the sound below 5Krpm as a little bonus.